Just looking for some input into a chain line issue I'm having on my Cannondale supersix, as the chain rubs the inside of the larger chainring when in 39 x 14 or lower:

The Setup:- Cannondale Supersix HiMod 2010 frame- Cannondale Hollowgram SL crankset with BB30 - originally installed on a system six, the frame cracked and was replaced with the super six, all parts carried over- 3 x 0.5m shims are installed between bearing shield and wave washer (note that instructions say upto 5 can be used - http://media.cannondale.com/media/Manua ... ent_en.pdf)- Fulcrum racing 1 hub running shimano ultegra 12-15 cassette, using the 1mm spacer as supplied with shimano hubs- 39/53 front chainrings- sram force for remaining group set

The Issue:- The chain line seems too far inboard at the crankset relative to the rear cassette- The main problem is that when I am in the small chain ring, the chain rubs against the inside of the big chain ring when in 14,13 or 12 on the rear cassette (note it does not rub the front derailleur, it is definitely the chain ring)

The questions for WW experts:- Has anyone else come across this issue?- Would adding 2 more shims to the crankset be likely to solve the issue, or just compress the wave washer too much?- Any other thoughts? e.g.I could remove or reduce the size of the 1mm spacer on the cassette, however then spoke clearance will likely be an issue.

I don't usually run 39 x 12 or 13, but not having the 39 x 14 is a bit of a pain.

You'll undoubtably get a better anwswer from someone else but yes that seems to be a pretty common proble. The good news is that the new SiSl2 road axle is a touch wider so using it should help. Also 11 speed chains work fine on 10 speed set ups and are just a touch narrower so that should help.

I would second the thought about the 109mm SiSL2 spindle. While my issues were related to clearance of the inner face of a Hollowgram SRM, I got a SiSL2 spindle which Cannondale removed the non-drive side 'shoulder', which along with moving the wave spring washer and adding a 2.5mm spacer to the non-drive side, allows for more adjustment of the chainline in terms of adding drive side spacer. If you want a lower cost option, take your current spindle to a machine shop and have the shoulder machined off which gives you more room to play with in terms of adding drive side spacers.

I would second the thought about the 109mm SiSL2 spindle. While my issues were related to clearance of the inner face of a Hollowgram SRM, I got a SiSL2 spindle which Cannondale removed the non-drive side 'shoulder', which along with moving the wave spring washer and adding a 2.5mm spacer to the non-drive side, allows for more adjustment of the chainline in terms of adding drive side spacer. If you want a lower cost option, take your current spindle to a machine shop and have the shoulder machined off which gives you more room to play with in terms of adding drive side spacers.

I would do exactly the same. I have had the same clearance issues with my SystemSix and the new 3D hollowgrams and this method worked. Although follow the sisl2 instructions for install and use extra 2.5 (sram shims work fine) shims where they show the thick shim on the non-drive side since that shim is only available with the press fit kit.

Although follow the sisl2 instructions for install and use extra 2.5 (sram shims work fine) shims where they show the thick shim on the non-drive side since that shim is only available with the press fit kit.

That is interesting. I wonder why the 2.5mm spacer is omitted for the BB30 bottom bracket kit? I have installed this PF30 SiSL2 kit ordered from InfiniteCycles for my SRM Hollowgram on a Raleigh RXC Pro disc but only ordered the SiSL2 spindle for my BB30 bike. Infinite must be making these up custom as I note that the 2.5mm spacer is also included with the ceramic BB30 kit.

It's rare when a double crank doesn't have the nearly universal (but stupid) 43.5mm chainline. The 43.5mm is measured from the center of the seat tube to a point centered between the two chainrings. It's tough to measure a point out in space. Knowing that typical chainring spacing is 7.5-8mm, just add or subtract half of that to 43.5mm and measure to the tip of a tooth on the big or little ring. The little ring should measure about 39.5mm or slightly more. It's more accurate to measure from the side of the tube and subtract half the tube diameter, except when the tube is not round and the "diameter" is unknown.

Thanks all. So it seems the recommended fix to use a different crankset (I.e. SiSL2) or to machine the existing one. Am i right in guessing that adding two more shims will just compress the wave washer more and not improve the chain line significantly?

The problem with adding shims as I discovered is if the crank is not seated correctly over the end of the spindle it will put all the stress on the outer bolt which goes against the design. I learned that by trying to deviate from the install directions myself.

I am using the new spindle now with the new 3d forged cranks. The spacer kit is the same as others with the exception of the thicker spacer for the non-driveside and ceramic bearings. The new spider chain ring should mount exactly as the the old spider did. The only reason I did not use the new spider chain ring is because I use rotor rings.

Bringing up this old discussion. Just installed a new SISL2 with 109 spindle and correct spacer kit on a new PF30 frame. The frame is perfectly straight and BB is a spot on 68.2mm wide and correctly centered in the frame(ask me how I know).

Followed the Dale instruction to a T. 2.5 driveside spacer, larger NDside spacer, correct PF30 dust covers, all is good. Bike shifts fine but I don't like the chain line and worse than that the Q of the driveside is exactly 5mm further from frame center than the NDS. Conventional wisdom says move the 2.5 spacer to the NDS and viola, perfect Q balance and perfect chain line.

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